iPhone 6 and 6 Plus Equipped With Two Accelerometers for Power Management, Improved User Experience

Apple has opted to equip the iPhone 6 and 6 Plus with two separate accelerometers, as discovered in Chipworks' comprehensive iPhone 6 and 6 Plus teardown. There's a three-axis Bosch BMA280 accelerometer and what Chipworks believes is a MPU-6700 six-axis accelerometer from InvenSense.

According to Chipworks, Apple may have decided to incorporate two accelerometers into the iPhone 6 and 6 Plus to both minimize power consumption and "improve the overall user experience."

The InvenSense accelerometer has a range of functions, allowing it to operate in several different modes, but it can draw more power than the Bosch accelerometer due to its higher sensitivity. The maximum sensitivity of the InvenSense is at 16684 LSB/g, much higher than the Bosch's 4096.

The InvenSense device can operate as a six axis inertial sensor, or as either a three-axis gyroscope or a three-axis accelerometer. It is rated to consume 3.4 mA in the six-axis mode, 3.2 mA in the gyroscope mode and 450 µA in the accelerometer normal mode. By contrast, the Bosch device operates as a 3-axis accelerometer only and it consumes 130 µA of current in the accelerometer normal mode. Both devices offer two low power levels of operation for the accelerometer function. The InvenSense device actually consumes less current in its lowest power mode, with a 1 Hz update rate.

The main benefit of the InvenSense is full six-axis integration of the data by the on-chip digital motion processor (DMP). This will provide a direct benefit for gaming and other applications that need sophisticated inertial sensing capabilities. In addition the InvenSense provides significantly higher sensitivity than the Bosch device. The price however, is higher power consumption.

The Bosch accelerometer is able to operate at a lower power than the InvenSense and it has a "much faster" cold start up time, at 3ms compared to 30ms, allowing it to be used when complete six-axis integration is unnecessary. Chipworks speculates that it may be used for tasks where higher sensitivity is unneeded, perhaps for rotating the screen from landscape to portrait mode or for pedometer functionality.

According to Chipworks, the inclusion of two accelerometers in the iPhone 6 and 6 Plus is an example of Apple's "elegant engineering." A single InvenSense accelerometer would have enabled the device to work perfectly well, but the addition of the Bosch accelerometer allows for lower power consumption in the appropriate situations.

OK, so I got the obvious, witty Android joke out of the way. Here's the real point:

A lot of people look at these devices being released every year with the sense that all these companies do (LG, Samsung, and others included) is slap the same old components on the inside and change the case or screen size. In reality, they are re-architecting a lot of the technology every year or two. This is not easy to do.

Only when we get tear downs and such do we get the full story of everything going on inside the shell. These guys are doing amazing work to move technology forward. The result is better devices and increased convenience/utility for the user.

The engineers that put this particular solution together aren't going to be recognized or win any awards, but they're doing great things.

It is exactly this type of clever engineering which is why Apple don't need to include 2Gb of ram just to look good in the specs race.

Hmm, well then explain the very frequent reloading of Safari tabs, apps losing their state when multitasking between more than just 2-3 apps, don't dare to use background tasks like music players or something...

Some people seem to know for certain that Android is just as efficient with RAM as iOS. They also seem to know for certain that RAM does not affect battery life. Thus, they are certain that more RAM is ALWAYS better, and that there is NO compromise involved, and NO benefit to less-than-2-GB RAM beyond greed.

What are the sources for these details? Or are they really just making assumptions? (Like assuming a 4-core Android phone performs tasks faster than a 2-core A8, when the reality is the reverse?)

I love a bullet-point marketing spec number as much as the next nerd, and would LOVE to hear an iPhone had 2GB, or 200 GB... but I love real-world functionality so much more. If one spec number has to go down for another to go up, that's just reality. 90s-style spec wars help nobody if we don't look at the big picture of what the device delivers for the user. Software plus hardware in the real world, targeting the most common uses over less common ones. Very complex--although we humans don't tend to like complexity! We wish the world were black and white, and no decision were ever a trade-off.

Hmm, well then explain the very frequent reloading of Safari tabs, apps losing their state when multitasking between more than just 2-3 apps, don't dare to use background tasks like music players or something...

2) Most apps are written badly. They consume vastly more amounts of RAM than they should because the devs were too lazy to cache things effectively. Apple has an energy meter in iOS 8 for power-hungry apps, but they should also put a RAM usage meter in there to shame these developers.

So, if developers did their jobs properly and conformed to Apple's best practices, 1GB would be adequate. But they're lazy and are often given short deadlines to launch products/features. And if Apple gives us 2GB devices, the developers will just be more lazy. Developer laziness expands proportionally to the amount of slack given to them. So then soon you'll be clamoring for 4GB.

I'm not arguing we don't need 2GB of RAM, but what we also need is more efficiency.

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